The present invention relates to an expansion valve for controlling the flow rate of a refrigerant to be supplied to an evaporator in a refrigeration cycle of a refrigerator, an air conditioning device and so on.
This type of expansion valve is used in the refrigeration cycle of an air conditioning device in vehicles and the like, as well-known in the prior art. FIG. 4 shows one example of a vertical cross-sectional view of a widely used prior art expansion valve together with an outline of the refrigeration cycle. FIG. 5 is a schematic view of the valve body in the expansion valve, and FIG. 6 is a front view of the expansion valve of FIG. 4 viewed from direction A. The expansion valve 10 comprises a valve body 30 made of aluminum and having a substantially prismatic shape, to which are formed a first passage 32 of a refrigerant pipe 11 in the refrigeration cycle mounted in the portion from the refrigerant exit of a condenser 5 through a receiver 6 toward the refrigerant entrance of an evaporator 8 through which a liquid-phase refrigerant travels, and a second passage 34 of the refrigerant pipe 11 mounted in the portion from the refrigerant exit of the evaporator 8 toward the refrigerant entrance of a compressor 4 through which a gas-phase refrigerant travels. The passages are formed so that one passage is positioned above the other passage with a distance in between. Further, in FIGS. 5 and 6, reference number 50 show bolt inserting holes for mounting the expansion valve 10.
On the first passage 32 is formed an orifice 32a where adiabatic expansion of the liquid-phase refrigerant supplied from the refrigerant exit of the receiver 6 is to be performed. On the entrance side of the orifice 32a or upper stream side of the first passage is formed a valve seat, and a spherical valve means 32b supported by the valve member 32c from the upper stream side is positioned on the valve seat. The valve member 32c is fixed to the valve means by welding, and positioned between a biasing means 32d of a compression coil spring and the like, thereby transmitting the bias force of the biasing means 32d to the valve means 32b, and as a result, biasing the valve means 32b toward the direction approaching the valve seat. By the above-mentioned operation, the opening of the valve is adjusted.
The first passage 32 to which the liquid-phase refrigerant from the receiver 6 is introduced acts as the passage for the liquid-phase refrigerant. An entrance port 321 connected to the receiver 6 and a valve chamber 35 connected to the entrance port 321 is formed to the valve body 30, wherein a valve means 32b is positioned inside the valve chamber 35. An exit port 322 is connected to the evaporator 8. The valve chamber 35 is a chamber with a bottom formed coaxially with the orifice 32a, and is sealed by a plug 39, which acts as an adjusting screw. The plug 39 is movably screwed in the advancing or retreating direction onto a mounting hole 39xe2x80x2 communicated to the valve chamber 35, for controlling the pressurizing force of the coil spring. The plug 39 is equipped with an o-ring 39a, so as to secure the sealed state between the valve body 30.
Moreover, the valve body 30 is equipped with a small radius hole 37 and a large radius hole 38, which is larger than the hole 37, which penetrate through the second passage 34 and are positioned coaxial to the orifice 32a, so as to provide driving force to the valve means 32b for opening or closing the orifice 32a according to the exit temperature of the evaporator 8. On the upper end of the valve body 30 is formed a screw hole 361 to which a power element portion 36 acting as a heat sensing portion is fixed.
The power element portion 36 comprises a diaphragm 36a made of stainless steel, an upper cover 36d and a lower cover 36h welded to each other with the diaphragm 36a positioned in between so as to each define an upper pressure housing 36b and a lower pressure housing 36c forming two sealed housings on the upper and lower areas of the diaphragm 36a, and a sealed tube 36i for sealing a predetermined refrigerant working as a diaphragm drive liquid into the interior space communicated to the upper pressure housing 36b, wherein the lower cover 36h is screwed onto the screw hole 361 with a packing 40. The lower pressure housing 36c is communicated to the second passage 34 through a pressure-equalizing hole 36e formed coaxial to the center axis of the orifice 32a. The refrigerant vapor from the evaporator 8 flows through the second passage 34, and therefore, the second passage 34 acts as a passage for the gas-phase refrigerant, and the pressure of the refrigerant gas is loaded to the lower pressure housing 36c through the pressure-equalizing hole 36e. Further, reference number 342 represents an entrance port from which the refrigerant transmitted from the evaporator 8 enters, and 341 represents an exit port from which the refrigerant to be transmitted to the compressor 4 exits. In FIGS. 5 and 6, the sealed tube 36i is omitted from the drawing.
Inside the lower pressure housing 36c contacting the diaphragm 36a is formed an aluminum heat sensing shaft 36f positioned slidably inside the large radius hole 38 penetrating the second passage 34, so as to transmit the refrigerant exit temperature of the evaporator 8 to the lower pressure housing 36c and to slide inside the large radius hole 38 in correspondence to the displacement of the diaphragm 36a accompanied by the difference in pressure between the lower pressure housing 36c and the upper pressure housing 36b in order to provide drive force, and a stainless steel operating shaft 37f having a smaller diameter than the heat sensing shaft 36f is positioned slidably inside the small radius hole 37 for pressing the valve means 32b in resistance to the elastic force of the biasing means 32d according to the displacement of the heat sensing shaft 36f, wherein the heat sensing shaft 36f is equipped with a sealing member, for example, an o-ring 36g, so as to secure the seal between the first passage 32 and the second passage 34. The upper end of the heat sensing shaft 36f contacts to the lower surface of the diaphragm 36a as the receiving portion of the diaphragm 36a, the lower end of the heat sensing shaft 36f contacts to the upper end of the operating shaft 37f, and the lower end of the operating shaft 37f contacts to the valve means 32b, wherein the heat sensing shaft 36f together with the operating shaft 37f constitute a valve drive shaft. Accordingly, the valve drive shaft extending from the lower surface of the diaphragm 36a to the orifice 32a of the first passage 32 is positioned coaxially inside the pressure-equalizing hole 36e. Further, a portion 37e of the operating shaft 37f is formed narrower than the inner diameter of the orifice 32a, which penetrates through the orifice 32a, and the refrigerant passes through the orifice 32a. 
A known diaphragm drive liquid is filled inside the upper pressure housing 36b of the pressure housing 36d, and through the diaphragm 36a and the valve drive shaft exposed to the second passage 34 and the pressure equalizing hole 36e communicated to the second passage 34, the heat of the refrigerant vapor travelling through the second passage 34 from the refrigerant exit of the evaporator 8 is transmitted to the diaphragm drive liquid.
In correspondence to the heat being transmitted as above, the diaphragm drive liquid inside the upper pressure housing 36b turns into gas, the pressure thereof being loaded to the upper surface of the diaphragm 36a. The diaphragm 36a is displaced to the vertical direction according to the difference between the pressure of the diaphragm drive gas loaded to the upper surface thereof and the pressure loaded to the lower surface thereof.
The vertical displacement of the center area of the diaphragm 36a is transmitted to the valve means 32b through the valve drive shaft, which moves the valve means 32b closer to or away from the valve seat of the orifice 32a. As a result, the flow rate of the refrigerant is controlled.
The temperature of the low-pressure gas-phase refrigerant sent out from the exit of the evaporator 8 is transmitted to the upper pressure housing 36b, and according to the temperature, the pressure inside the upper pressure housing 36b is changed. When the exit temperature of the evaporator 8 rises, in other words, when the heat load of the evaporator is increased, the pressure inside the upper pressure housing 86b is raised, and correspondingly, the heat sensing shaft 36f or valve drive shaft is driven to the downward direction, pushing down the valve means 32b. Thereby, the opening of the orifice 32a is widened. This increases the amount of refrigerant being supplied to the evaporator 8, and lowers the temperature of the evaporator 8. In contrast, when the temperature of the refrigerant sent out from the evaporator 8 is lowered or heat load of the evaporator is reduced, the valve means 32b is driven to the opposite direction, narrowing the opening of the orifice 32a, reducing the amount of refrigerant being supplied to the evaporator, and raises the temperature of the evaporator 8.
In this type of expansion valves, it is preferable that only the liquid-phase refrigerant from the receiver 6 be supplied thereto. However, the gas-phase refrigerant may be mixed to the liquid-phase refrigerant inside the receiver, and there are cases where a gas-liquid phase refrigerant is transmitted to the entrance port 321. In such case, when the refrigerant including the gas-phase refrigerant travels from the entrance port 321 through the valve chamber 35 and the orifice 32a toward the exit port 322, refrigerant passage noise may be generated.
The present invention aims at providing an expansion valve solving the above-mentioned problem.
In order to solve the problem, the expansion valve according to the present invention comprises a valve body, a valve chamber formed inside said valve body to which a refrigerant enters from a passage where high-pressure refrigerant being transmitted to an evaporator travels, a valve means positioned inside said valve chamber for adjusting the flow rate of said refrigerant, said valve means being driven according to the temperature of a low-pressure refrigerant transmitted from said evaporator to a compressor, wherein said valve chamber includes a throttle portion formed so as to interfere with said passage, and through said throttle portion enters said refrigerant into said valve chamber.
Further, the expansion valve according to the present invention comprises a valve body including a first passage through which a high-pressure refrigerant flowing toward an evaporator travels and a second passage through which a low-pressure refrigerant flowing from said evaporator toward a compressor travels, a valve means being driven according to the temperature of said low-pressure refrigerant by a power element portion mounted to an upper end portion of said valve body, a mounting hole formed to a bottom end portion of said valve body to which an adjustment screw is movably mounted in the advancing or retreating direction for adjusting the pressurizing force of a spring for controlling the valve opening of said valve means, and a valve chamber defined by a passage being communicated to said mounting hole, wherein said expansion valve further comprises a throttle portion formed by said passage defining said valve chamber being interfered with said first passage, and through said throttle portion flows said high-pressure refrigerant traveling from said first passage into said valve chamber.
Even further, the expansion valve according to the present invention characterized in that said first passage is formed so that the diameter thereof is reduced gradually toward said valve chamber, and a wall portion is formed to the area between said first passage and said valve chamber.
As above, by forming a throttle portion connecting the first passage and the valve chamber, the bubbles inside the refrigerant may be fined, and as a result, the noise level of the refrigerant passage noise caused by the existence of bubbles may be reduced.